Prenatal exposure to very high levels of “forever chemicals” may increase the risk of asthma in children, according to a Swedish study.
Researchers analysed data from more than 11,000 children born between 2006 and 2022 in southern Sweden, where some communities were exposed to extremely high levels of per- and polyfluoroalkyl substances (PFAS) due to contaminated water supplies.
They found that children whose mothers were exposed to very high levels of PFAS during pregnancy were more likely to be diagnosed with asthma. No clear link was found at lower exposure levels, and there was no association between PFAS exposure and wheezing.
PFAS are a large group of synthetic chemicals used in products such as firefighting foams, non-stick cookware, and water-resistant materials. They are known as “forever chemicals” because they do not break down easily in the environment or the human body, and have been linked to a range of health concerns, including their adverse effect on the immune system.
The study, published in PLOS Medicine, drew on a natural experiment in the town of Ronneby, where drinking water was heavily contaminated for years by firefighting foam used at a nearby military site. This resulted in exposure levels “hundreds of times higher than the general population”, according to the researchers.
“We found that children whose mothers were exposed to very high levels of PFAS during pregnancy had a substantially higher incidence of clinically diagnosed asthma,” the authors said, adding that the absence of effects at lower levels may help explain why earlier studies have shown mixed results.
They described PFAS contamination as “a major source of high environmental exposure globally” and said the findings point to “a substantial and previously unrecognised public health consequence”.
PFAS contamination has prompted tighter regulation in parts of Europe and the US in recent years, amid concerns about their persistence in water supplies and potential long-term health effects.
Independent experts said the results highlight risks at extreme exposure levels, but cautioned against extrapolating them to the general population.
Associate professor Peter Franklin, who is a respiratory epidemiologist at the University of Western Australia and was not involved in the study, said the increased risk was seen only in the highest exposure group.
“The average potential PFAS concentrations in mothers in the ‘very high’ exposure group were many times greater than what has been found in the general population,” he said, noting that even communities near known contamination sites in Australia had lower exposure levels.
He added that the study relied on estimated exposure based on residential location rather than individual measurements, and said “the effects of low-level exposure, if any, are still unclear”.
PFAS contamination has been detected in water supplies around the world, often linked to industrial activity and firefighting foams, raising ongoing concerns about long-term health impacts, particularly for vulnerable groups such as pregnant women and children.
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